Print circuit board

Abstract

There is disclosed a wiring substrate comprising a wiring circuit pattern formed on a metal substrate with an insulating resinous layer interposed therebetween. In this wiring substrate, the insulating resinous layer is formed of a high molecular composition comprising thermosetting 1,2-polybutadiene containing 5 to 30% by weight of a high molecular softening agent such as hydrogenated polybutadiene. A method of manufacturing such a wiring substrate is also disclosed, wherein a light-reflecting pigment is included in the insulating resinous layer for the convenience of the subsequent laser trimming.

What is claimed is: 
     
       1. A wiring substrate comprising a wiring circuit formed on a metal substrate with an insulating resinous layer interposed therebetween, wherein said insulating resinous layer is formed of a high molecular composition comprising thermosetting 1,2-polybutadiene containing 5 to 30% by weight (based on the whole mass of the resinous layer) of high molecular softening agent. 
     
     
       2. The wiring substrate according to claim 1, wherein the high molecular softening agent is hydrogenated polybutadiene or atactic polypropylene resin. 
     
     
       3. The wiring substrate according to claim 1, wherein the high molecular softening agent is one selected from the group consisting of chlorinated polyethylene, ethylene-vinyl acetate copolymer, and vinyl acetate. 
     
     
       4. The wiring substrate according to claim 1, wherein the thermosetting 1,2-polybutadiene resin has an average molecular weight of 1700 to 3300. 
     
     
       5. The wiring substrate according to claim 1, wherein the metal substrate is prepared from aluminium. 
     
     
       6. The wiring substrate according to claim 1, wherein the insulating resinous layer further contains light-reflecting pigment. 
     
     
       7. The wiring substrate according to claim 1, wherein the insulating resinous layer further contains thixotropic agent. 
     
     
       8. The wiring substrate according to claim 1, wherein the insulating resinous layer further contains a solvent. 
     
     
       9. The wiring substrate according to claim 1, wherein the insulating resinous layer has a lower relative dielectric constant than 3. 
     
     
       10. The wiring substrate according to claim 1, which further comprises another insulating resinous layer interposed between said wiring circuit and said insulating resinous layer, said another insulating resinous layer comprising thermosetting 1,2-polybutadiene and containing no softening agent.